diff -r 8f5825e0aeaa -r 3f06f139ef53 src/cpu/x86/vm/interp_masm_x86_64.cpp
--- a/src/cpu/x86/vm/interp_masm_x86_64.cpp	Fri Jun 26 13:03:29 2009 -0700
+++ b/src/cpu/x86/vm/interp_masm_x86_64.cpp	Fri Jun 26 16:14:31 2009 -0700
@@ -1409,6 +1409,8 @@
     // If no method data exists, go to profile_continue.
     test_method_data_pointer(mdp, profile_continue);
 
+    set_mdp_flag_at(mdp, BitData::null_seen_byte_constant());
+
     // The method data pointer needs to be updated.
     int mdp_delta = in_bytes(BitData::bit_data_size());
     if (TypeProfileCasts) {